1. Field of the Invention
The present invention relates generally to a fan frame body structure, and more particularly to an anti-relief fan frame body structure, which can increase the performance of the fan.
2. Description of the Related Art
Following the rapid development of high-performance, high-frequency, high-speed and slimmed electronic products, the electronic products generate more and more heat in operation. As a result, the electronic products are likely to operate unstably. This will affect reliability of the products and shorten lifetime of the products. Therefore, it has become a critical issue how to dissipate the heat generated by the electronic products. In general, a cooling fan is often used as a heat dissipation for dissipating the heat generated by the electronic products
When a conventional cooling fan operates, eddy is often formed between the blades of the fan. The eddy will cause deterioration of the performance (such as air volume) of the fan. To solve this problem, an annular fan has been developed.
Please refer to FIGS. 1A and 1B. The conventional annular fan 1 includes a frame body 10 and a fan impeller 11. The frame body 10 has a wind outlet side 101, a wind inlet side 102 opposite to the wind outlet side 101 and a bearing cup 104.
The wind outlet side 101 and the wind inlet side 102 together define a receiving space 12 for receiving the fan impeller 11 therein. The bearing cup 104 is positioned at a center of the receiving space 12. The fan impeller 11 is rotatably disposed in the bearing cup 104.
The fan impeller 11 has a hub 111 and multiple blades 112 annularly arranged along outer circumference of the hub 111. Each blade 112 has a free end. An annular body 14 is connected to the free ends of the blades 112. A gap 15 is defined between the annular body 14 and inner circumference of the frame body 10. When the fan operates, the annular body 14 is able to reduce the eddy between the blades so as to increase the performance of the fan.
In the conventional annular fan 1, the annular body 14 serves to overcome the problem of generation of the eddy. However, the annular body 14 leads to another problem. In operation of the annular fan 1, the fluid is guided in from the wind inlet side 102 and then guided out from wind outlet side 101. At this time, a negative pressure is created on the wind outlet side 101. Accordingly, part of the guided out fluid 17 will flow back through the gap 15 to interfere with the guided in fluid to produce turbulence. As a result, the fluid can hardly flow smoothly. This will lead to deterioration of the performance of the fan and make great noise.
According to the above, the conventional fan has the following shortcomings:
1. The performance of the fan is deteriorated.
2. The fan will make great noise in operation.